Public Abstract

DE-SC0001136: Computational studies of magnetism and spectra of actinide complexes

Award Status: Active

Institution: Research Foundation for the State University of New York d/b/a RFSUNY - University at Buffalo, Amherst, NY
UEI: LMCJKRFW5R81
DUNS: 038633251

Most Recent Award Date: 06/16/2026
Number of Support Periods: 17
PM: Wilk, Philip

Current Budget Period: 08/15/2026 - 08/14/2027
Current Project Period: 08/15/2024 - 08/14/2027
PI: Autschbach, Jochen

Supplement Budget Period: N/A

Public Abstract

This project is concerned with theoretical studies of magnetic and spectroscopic properties of molecules containing very heavy metal atoms, namely coordination compounds of actinides ("5f" metals). A major goal of the project is the prediction and analysis of magnetic and spectroscopic properties for actinide complexes that are encountered in the nuclear fuel cycle and in other forms. Where appropriate, calculations may also be performed on lanthanide ("4f") analogs or transition metal model systems. The project focuses on a broad range of spectroscopic and magnetic properties of actinide compounds that are used by experimental teams to characterize their molecular structure and bonding. Actinide chemistry is a frontier, and it is extremely important both for applied as well as fundamental science. Theoretical support in this area is vital in order to advance the state of the art. Specifically, this project focuses on the extent of covalent chemical bonding in 5f metal complexes, their electronic spectra at X-ray and optical wavelengths, nuclear magnetic resonance (NMR) parameters and their relations to structure and bonding in actinide complexes, and Mössbauer spectroscopic parameters for neptunium-237. Calculations of electron paramagnetic resonance spectroscopic parameters, nuclear quadrupole resonance parameters, and the magnetic susceptibility, will also be carried out as needed. These properties will be calculated from first principles quantum theory and analyzed to understand how they relate to molecular structure and to the chemical bonding in the electronic ground state and in the excited states. The various magnetic and spectroscopic properties are affected in different ways by molecular structure and bonding, and therefore they reveal complementary information. Experimental magnetic and quadrupole resonance, Mössbauer, and electronic spectra of actinide compounds can be very difficult if not impossible to interpret without theoretical support. The theoretical studies in this project will reveal a wealth of information about the chemical behavior and chemical transformations of actinide compounds as they are monitored via their magnetic and spectroscopic properties. The project involves development and applications of quantum-theoretical methods for the study of the properties of heavy-metal complexes with unpaired electrons (the metal atoms are said to have 'open shells'). This is a frontier in theoretical chemistry. A crucial aspect of these computational methods is their ability to describe open-shell metal complexes with thermally accessible magnetic electronic states. Part of the project's efforts are directed at developing new theoretical methods to render calculations of the magnetic and spectroscopic properties of open-shell actinide complexes feasible in the first place, and to improve the accuracy of such calculations. A theoretical understanding of the magnetic and spectroscopic properties of actinide compounds is a critical ingredient for the exploration of 5f-element chemistry. Some types of calculations that are going to be performed in this project have never been attempted. Beyond the specific outcomes of the computational studies, new quantum chemical development will be made available to the scientific community as part of widely utilized open-source quantum chemistry packages, for example NWChem and Molcas, and stand-alone open-source tools. NWChem and Molcas are state-of-the-art computational tools for f-element compounds. These developments will also have an impact beyond the actinide field because these programs are applicable to all types of molecules with elements across the periodic table. Collaborative scientific projects with other Department of Energy researchers are under way to utilize these theoretical methods.

This project is concerned with theoretical studies of magnetic and spectroscopic properties of molecules containing very heavy metal atoms, namely coordination compounds of actinides ("5f" metals). A major goal of the project is the prediction and analysis of magnetic and spectroscopic properties for actinide complexes that are encountered in the nuclear fuel cycle and in other forms. Where appropriate, calculations may also be performed on lanthanide ("4f") analogs or transition metal model systems. The project focuses on a broad range of spectroscopic and magnetic properties of actinide compounds that are used by experimental teams to characterize their molecular structure and bonding. Actinide chemistry is a frontier, and it is extremely important both for applied as well as fundamental science. Theoretical support in this area is vital in order to advance the state of the art. Specifically, this project focuses on the extent of covalent chemical bonding in 5f metal complexes, their electronic spectra at X-ray and optical wavelengths, nuclear magnetic resonance (NMR) parameters and their relations to structure and bonding in actinide complexes, and Mössbauer spectroscopic parameters for neptunium-237. Calculations of electron paramagnetic resonance spectroscopic parameters, nuclear quadrupole resonance parameters, and the magnetic susceptibility, will also be carried out as needed. These properties will be calculated from first principles quantum theory and analyzed to understand how they relate to molecular structure and to the chemical bonding in the electronic ground state and in the excited states. The various magnetic and spectroscopic properties are affected in different ways by molecular structure and bonding, and therefore they reveal complementary information.

Experimental magnetic and quadrupole resonance, Mössbauer, and electronic spectra of actinide compounds can be very difficult if not impossible to interpret without theoretical support. The theoretical studies in this project will reveal a wealth of information about the chemical behavior and chemical transformations of actinide compounds as they are monitored via their magnetic and spectroscopic properties.

The project involves development and applications of quantum-theoretical methods for the study of the properties of heavy-metal complexes with unpaired electrons (the metal atoms are said to have 'open shells'). This is a frontier in theoretical chemistry. A crucial aspect of these computational methods is their ability to describe open-shell metal complexes with thermally accessible magnetic electronic states. Part of the project's efforts are directed at developing new theoretical methods to render calculations of the magnetic and spectroscopic properties of open-shell actinide complexes feasible in the first place, and to improve the accuracy of such calculations.

A theoretical understanding of the magnetic and spectroscopic properties of actinide compounds is a critical ingredient for the exploration of 5f-element chemistry. Some types of calculations that are going to be performed in this project have never been attempted. Beyond the specific outcomes of the computational studies, new quantum chemical development will be made available to the scientific community as part of widely utilized open-source quantum chemistry packages, for example NWChem and Molcas, and stand-alone open-source tools. NWChem and Molcas are state-of-the-art computational tools for f-element compounds. These developments will also have an impact beyond the actinide field because these programs are applicable to all types of molecules with elements across the periodic table. Collaborative scientific projects with other Department of Energy researchers are under way to utilize these theoretical methods.